1. Field of the Invention
The present invention relates to a biopsy apparatus, which is incorporated in a radiographic image capturing apparatus for capturing radiographic images of an object to be examined, and which operates by inserting a biopsy needle into a biopsy region of an object to be examined and sampling tissue from the biopsy region.
2. Description of the Related Art
There have heretofore been developed biopsy apparatus for sampling tissue of a biopsy region in an object to be examined of a subject and thoroughly examining the sampled tissue to perform a disease diagnosis. Such a biopsy apparatus often is incorporated in a radiographic image capturing apparatus. The radiographic image capturing apparatus applies radiation to an object to be examined in different directions in order to capture a plurality of radiographic images of a biopsy region in a stereographic image capturing process. The biopsy apparatus determines the three-dimensional position of the biopsy region from the acquired radiographic images, moves a biopsy needle to the biopsy region based on the determined three-dimensional position, and samples tissue from the biopsy region with the biopsy needle.
It is assumed that when tissue is sampled from a biopsy region in a subject's breast as the object to be examined, the breast is placed on an image capturing base, which houses therein a radiation detector for converting radiation into a radiographic image. The breast is compressed against the image capturing base by a compression plate, which is displaced toward the image capturing base.
The biopsy apparatus samples tissue from the biopsy region in the breast by inserting the biopsy needle into the breast through an opening defined in the compression plate. In the art, there are different processes for inserting the biopsy needle into the breast. They include (1) a process for inserting the biopsy needle into the breast along a direction in which the compression plate compresses the breast (in the description of the related art, this process will be referred to as “vertical piercing”) and (2) a process for inserting the biopsy needle into the breast while the biopsy needle is oriented obliquely to the direction in which the compression plate compresses the breast (in the description of the related art, this process will be referred to as “oblique piercing”). Commercially available biopsy apparatus, which are presently available in the market, sample tissue from a biopsy region according to either one of the processes (1) or (2). The biopsy needle has a sampler for sampling tissue under suction, at a position that is slightly offset from the tip end thereof toward the proximal end thereof.
A biopsy apparatus that operates according to the vertical piercing process is capable of sampling tissue from a biopsy region in a breast that is relatively thick. However, when the sampler of the biopsy needle is aligned with a biopsy region in a relatively thin breast and the biopsy needle is inserted into the biopsy region, the tip end of the biopsy needle tends to pierce through the relatively thin breast (see FIG. 13C of the accompanying drawings). According to the vertical piercing process, therefore, it is difficult to sample tissue from a region of a relatively thin breast, which is close to the image capturing base. In addition, the vertical piercing process fails to quickly sample breast tissue that is spread in a planar direction along the compression plate or the image capturing base.
The biopsy apparatus that operates according to the oblique piercing process is capable of sampling tissue from a region of a relatively thin breast, which is close to the image capturing base, because the biopsy needle is inserted obliquely into the breast. However, since the biopsy needle is inserted obliquely into the breast, the breast includes a dead zone (shown by hatching in FIGS. 13A and 13B of the accompanying drawings) from which tissue cannot be sampled, positioned below an outer circumferential area of the opening in the compression plate, regardless of the thickness of the breast. In order to sample tissue from the dead zone, it is necessary to release the breast from the compression plate, then position the breast so that the dead zone is placed at the center of the opening as viewed in plan, compress the breast again with the compression plate, and insert the biopsy needle obliquely into the breast. Therefore, in the oblique piercing process, it is necessary to repeat a sequence of successive steps of positioning the breast, compressing the breast, capturing an image of the breast, inserting the biopsy needle into the breast, sampling tissue from the breast, and releasing the breast, as many times as the number of tissues to be sampled from the dead zone. As a result, the subject is subjected to the examination procedure for a long period of time, and is exposed to an increased dose of radiation.
The vertical piercing process and the oblique piercing process are disclosed respectively in Japanese Laid-Open Patent Publication No. 01-256942, Japanese Laid-Open Patent Publication No. 07-504586 (PCT), Japanese Laid-Open Patent Publication No. 11-505446 (PCT), Japanese Laid-Open Patent Publication No. 2004-033753, and Japanese Laid-Open Patent Publication No. 2008-513090 (PCT), for example.
Because such conventional biopsy apparatus sample tissue from a biopsy region according to either one of the vertical piercing process or the oblique piercing process, as described above, such apparatus fail to sample tissue reliably and efficiently.